This invention refers to a proximity switch with a switching body that has a sensing area which is parallel to the target area and mounted on a parallel support base.
These kinds of proximity switches find application in increasing numbers in industrial production facilities, especially if they are fully automated and direct contactless switching signals are required. This kind of proximity switch is usually firmly mounted on a support base, and this means that the distance between the sensing area of the proximity switch and the target area in which the object is situated, which triggers a switching signal, is adjusted with potentiometers.
Proximity switches with long sensing ranges are flat in design and this means that the sensing area is larger than the construction height. In a proximity switch mounted on a metallic base, which is usually the case in production facilities, this design has substantial disadvantages. This is based on the fact that the electromagnetic field of the proximity switch is affected by the metallic mounting base. This influence causes problems, e.g., where in a production line the switch is required to sense a different target and the sensing distance needs to be adjusted with a potentiometer accordingly. This adjustment requires specially trained personnel because the electronic adjustment changes not only the switching distance of the proximity switch but the entire switching characteristics, e.g., temperature dependency and switching time. It happens frequently that authorized personnel are not able to adjust the switches correctly and have a tendency to adjust the switches to their maximum switching range, with the result that the switch becomes oversensitive and, with temperature changes, gives misleading signals. This causes down time, especially in fully automated production lines.
There are proximity switches with a fixed switching distance available which are mechanically adjusted towards the targets. However, they have only small sensing ranges. They are long, cylindrical designs of which one circular area is the sensing surface. They are mounted at an angle to the base area or, if sensing must be perpendicular to the base area, they are mounted in a deep hole into the base area. Such a proximity switch is only adjustable to changing operational conditions with substantial mounting and installation alterations.
This invention aims, therefore, to create a proximity switch with the aforementioned features, a switch with long switching range and a minimum of mechanical alterations, adjustable to changing target distances. This task is solved by the invention of mounting at least one mounting stud normal to the base area with its longitudinal axis to the target area on which the sensing body is directionally flexibly mounted between the base area and target area.
The proximity switch of the present invention is built with a fixed switching distance and adjustment takes place mechanically.
The switch has the advantage that it is less sensitive with respect to installation errors. It is also an advantage that the switch can be built in an encapsulated construction which is a protection against dirt and other environmental influences. Furthermore, by means of simple distance measurement, the correct switching distance to the target is easily determined. Shielding discs protect the switch so that at different positions the switching body is without interference caused by the mounting base area, thus preventing switching irregularities.
The adjustment to changing operational conditions can be made with a few simple alterations which even unskilled personnel are able to achieve.
Due to the mechanical adjustment possibility, the electronic adjustment by means of the potentiometer becomes obsolete. This is the practical advantage because maladjustment is no longer possible. There was a tendency, due to a great deal of maladjustment, to ban proximity switches from computer-programmed production processes, and with the present invention this stigma has been positively overcome.
It is a special feature of the invention that the switch can also be applied in locations such as rolling mills because a cooling medium can be filtered through the center recess of the mounting stud, thus providing, even at high ambient temperatures, temperature independency.
Other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing.